Might seem like a dumb question...but by...

The thru axle adapter clamps in the fork mount of an existing bike rack just as a standard fork would. Usually I will install the adapter with the bike on the ground and the adapter's tabs pointed down. Using this technique allows you to load the bike on the roof as you would any bike with a standard 9mm QR fork.

If your rack locks, that's great, you'll be able to lock your $59 adapter to your car. But the bike comes off with the same ease as removing your front wheel. If you want to use this adapter and lock your bike to the car you may want to consider a cable.